Draw custom borders for table spanning across more than one page in itext7

问题

If I do like it: How during work itext find out coordinates text?

Everything works. But if i create table more one page, nothing is drawn:

PdfDocument pdfDoc = new PdfDocument(new PdfWriter(dest));
        Document doc = new Document(pdfDoc);
        doc.add(new Paragraph("Table event"));
        Table table = new Table(UnitValue.createPercentArray(3)).useAllAvailableWidth();
        table.setNextRenderer(new DottedLineTableRenderer(table, new Table.RowRange(0, 0)));
        table.addCell(new Cell().add(new Paragraph("test\ntest\ntest\ntest\ntest\ntest\ntest\ntest\ntest\ntest\ntest\ntest\ntest\ntest\ntest\ntest\ntest\ntest\ntest\ntest\ntest\ntest\ntest\ntest\ntest\ntest\ntest\ntest\ntest\ntest\ntest\ntest\ntest\ntest\ntest\ntest\ntest\ntest\ntest\ntest\ntest\ntest\ntest\ntest\ntest\n" )).setBorder(Border.NO_BORDER));
        table.addCell(new Cell().add(new Paragraph("A2")).setBorder(Border.NO_BORDER));
        table.addCell(new Cell().add(new Paragraph("A3")).setBorder(Border.NO_BORDER));

        doc.add(table);
        doc.close();

Custom Renderer class:

 private class DottedLineTableRenderer extends TableRenderer {
    public DottedLineTableRenderer(Table modelElement, Table.RowRange rowRange) {
        super(modelElement, rowRange);
    }

    @Override
    public void drawChildren(DrawContext drawContext) {
        super.drawChildren(drawContext);
        PdfCanvas canvas = drawContext.getCanvas();
        canvas.setLineDash(3f, 3f);
        // first horizontal line
        CellRenderer[] cellRenderers = rows.get(0);
        canvas.moveTo(cellRenderers[0].getOccupiedArea().getBBox().getLeft(),
                cellRenderers[0].getOccupiedArea().getBBox().getTop());
        canvas.lineTo(cellRenderers[cellRenderers.length - 1].getOccupiedArea().getBBox().getRight(),
                cellRenderers[cellRenderers.length - 1].getOccupiedArea().getBBox().getTop());

        for (int i = 0; i < rows.size(); i++) {
            cellRenderers = rows.get(i);
            // horizontal lines
            canvas.moveTo(cellRenderers[0].getOccupiedArea().getBBox().getX(),
                    cellRenderers[0].getOccupiedArea().getBBox().getY());
            canvas.lineTo(cellRenderers[cellRenderers.length - 1].getOccupiedArea().getBBox().getRight(),
                    cellRenderers[cellRenderers.length - 1].getOccupiedArea().getBBox().getBottom());
            // first vertical line
            Rectangle cellRect = cellRenderers[0].getOccupiedArea().getBBox();
            canvas.moveTo(cellRect.getLeft(), cellRect.getBottom());
            canvas.lineTo(cellRect.getLeft(), cellRect.getTop());
            // vertical lines
            for (int j = 0; j < cellRenderers.length; j++) {
                cellRect = cellRenderers[j].getOccupiedArea().getBBox();
                canvas.moveTo(cellRect.getRight(), cellRect.getBottom());
                canvas.lineTo(cellRect.getRight(), cellRect.getTop());
            }
        }
        canvas.stroke();
    }
}

Can I fix it?

回答1:

The code you are using has many assumptions about how the implementation works internally in TableRenderer.

As in your code you are drawing a dashed border I must point you to DashedBorder class which you can already use out of the box:

Border customBorder = new DashedBorder(ColorConstants.RED, 2);
table.addCell(new Cell().add(new Paragraph("A2")).setBorder(customBorder));

You can also implement your custom border class in the following way:

private static class CustomBorder extends Border {
    protected CustomBorder(Color color, float width) {
        super(color, width);
    }

    @Override
    public void draw(PdfCanvas canvas, float x1, float y1, float x2, float y2, Side defaultSide, float borderWidthBefore, float borderWidthAfter) {
    }

    @Override
    public void drawCellBorder(PdfCanvas canvas, float x1, float y1, float x2, float y2, Side defaultSide) {
        canvas.
                saveState().
                setStrokeColor(transparentColor.getColor());
        transparentColor.applyStrokeTransparency(canvas);
        canvas.
                setLineDash(3, 3).
                setLineWidth(width).
                moveTo(x1, y1).
                lineTo(x2, y2).
                stroke().
                restoreState();
    }

    @Override
    public int getType() {
        return Border.DASHED;
    }
}

Then just create an instance and use it in setBorder:

 Border customBorder = new CustomBorder(ColorConstants.RED, 2);
 table.addCell(new Cell().add(new Paragraph("A2")).setBorder(customBorder));

来源：https://stackoverflow.com/questions/56092142/draw-custom-borders-for-table-spanning-across-more-than-one-page-in-itext7